1. Field of the invention.
The present invention relates to an integrated pump and meter, and in particular a pump/meter combination with at least one spindle for pumping and metering the flow of fluid.
2. Description of the related art.
Traditional fuel dispensers contain a separate fuel pump and meter. In addition, a fuel dispenser may contain an air separator system for removing air from the fuel prior to metering. An air separator removes dissolved gases which may be present in the fuel. It is necessary to remove these dissolved gases before metering the fuel in order-to achieve an accurate measurement of the volume of fuel to be dispensed. The pump supplies fuel from a fuel storage tank. The meter is traditionally located downstream from both the pump and the air separator system.
One limitation of many traditional fuel dispensers is the need for a separate pump and meter. Due to a need for accuracy, the use of a combination pump/meter has not been feasible. Current regulations require accuracy for fluid metering not previously achievable by traditional pump/meter units.
One factor which prevents traditional fuel dispensers from utilizing a combination pump/meter unit is the presence of dissolved gases within the fluid, which affects metering accuracy. Conventional air separator systems will typically only function properly when located at the outlet side of a fuel pump. This is due to the fact that fluid pressure on the outlet side of a pump is higher than pressure on the inlet of the pump. Due to this design limitation, however, current fuel dispensers cannot utilize a combination pump/meter system since it is necessary to have the air separator located between the pump and the meter.
A second factor which affects the accuracy of traditional spindle meters is the inability to accurately account for gap losses in the metering process. Gap losses are associated with fluid which passes between the spindle and the cylinder wall which houses the spindle. When fluid passes between the spindle and the cylinder wall, this gap loss fluid volume is not accounted. Consequently, metering error is introduced due to gap losses.
An additional disadvantage in the art of pumps and meters for fuel dispensers is the cost associated with manufacturing and installing two separate components.
What is needed in the art is an integrated pump and meter which pumps and accurately measures the volume of fluid to be dispensed.
According to the present invention, an integrated pump and meter pumps fluid and volumetrically measures the fluid flow for accurately measuring the fluid to be dispensed as a function of fluid flow.
The invention, in one form thereof, is an integrated pump and meter for pumping a fluid and metering fluid flow. The integrated pump and meter includes an inlet and an outlet. The fluid may proceed along a fluid axis. At least one spindle extends axially along the fluid flow axis. A motor is operatively associated with at least one spindle for effecting rotation of the spindle. Rotation of the spindle produces the fluid flow. A rotation sensor detects rotation of the spindle. In one further embodiment thereof, a pair of pressure sensors are disposed in proximity of the inlet and the outlet for measuring an inlet and outlet pressure, respectively. In an alternate embodiment, there are a separate pump spindle and meter spindle, whereby the pump is operatively associated with the pump spindle and the rotational sensor is operatively associated the meter spindle.
The invention, in another form thereof, is a method of simultaneously pumping fluid and metering fluid flow. The method includes the step of providing an integrated pump and meter having an inlet and an outlet and at least one spindle. The rotation of at least one spindle is monitored and a pressure difference is measured between an inlet pressure and an outlet pressure. The volume of fluid flow is determined as a function of a spindle rotation and pressure difference. In one particular embodiment, fluid is pumped by applying rotational energy to the spindle. In an alternate embodiment, the pump/meter includes two spindles, a pump spindle for pumping the fluid, and a meter spindle for metering the flow of fluid.
The invention, in yet another embodiment thereof, is a fuel dispenser which performs the functions of pumping a fluid and metering fluid flow. The fluid dispenser includes a hose with a nozzle and an output device. A pump/meter includes an inlet and an outlet. The fluid may proceed along a fluid flow axis. At least one spindle extends axially along the fluid flow axis. A motor is operatively associated with the spindle for effecting rotation of the spindle. Rotation of the spindle produces a fluid flow. A rotation sensor detects rotation of the spindle. In one further embodiment, a pair of pressure sensors are located in proximity of the inlet and outlet for measuring inlet and outlet pressure, respectively. In an alternate embodiment, computational means generates a flow volume signal. The computational means is operatively associated with the rotational sensor. The flow volume signal is operatively associated with the output device for displaying a volume of fluid to be dispensed.
One advantage of the present invention is the integration of a pump and a meter into a single unit. As a result, a single unit can be manufactured and installed into a fuel dispenser rather than two separate components. In addition, there is a cost saving associated with the manufacturing and installing a single unit rather than two separate components.
A second advantage of the present invention is the accuracy by which the pump/meter combination computes the volume of fuel to be dispensed. In one particular embodiment, pressure sensors are located at the inlet and outlet of a pump/meter. A gap loss attributed to fluid passing between the spindle cylinder wall and the spindle is computed as a function of pressure difference between the inlet and the outlet pressure of the pump/meter. As a result, accurate volumes can be calculated as a function of spindle rotation and a pressure difference between the inlet and outlet fluid pressures of the pump/meter.
A third advantage to the present invention is the use of a single spindle for both pumping and metering functions. Rotational energy is applied to the spindle which then provides for a fluid flow. A sensor is associated with the spindle for monitoring the spindle""s rotation. As a result, a volume of fluid dispensed is calculated as a function of spindle rotation.
One advantage of a single spindle pump/meter system is a decrease in parts and complexity of the unit. Consequently, there is a cost associated with decreasing the complexity and number of components.